Optical waveguides consist of a transparent waveguiding core surrounded by transparent materials of lower indices of refraction. Several general methods are utilized for the fabrication of optical waveguides.
In one method optical waveguides are formed by applying a dielectric material to a transparent substrate of lower refractive index.
In another method thermoplastic polymer substrates are embossed with a metal die in the desired waveguide pattern, and subsequently filled or coated with a polymerizable higher index liquid monomer.
In another method optical waveguides are formed by selectively altering the index of refraction of a bulk transparent material. One technique involves ion bombardment in which selected regions of increased refractive index are provided by generating a molecular disorder pattern in a bulk matrix. In another technique selected regions of increased refractive index are either photo-induced in sensitized polymeric materials such as poly(methyl methacrylate) as described in Appl. Phys. Lett., 16, 486 (I970), or electrically induced by diffusing a higher index dopant into a transparent material.
Optical waveguides fabricated in GaAs/AlGa structures by laser-assisted etching has been reported in Integrated and Guided-wave Optics, 1989 Technical Digest Series, 4, 64-67 (Optical Society of America).
Methods of fabricating organic optical waveguides are a newly evolving technology. There are inherent disadvantages in the practice of the various known methods, such as difficult multi-step procedures which do not provide reliable quality control and reproducibility. Typical organic waveguiding media exhibit high optical scattering losses.
Of particular interest with respect to the present invention is UK Patent Application GB 2-222-465-A which was published on Mar. 7, 1990. The patent application describes the fabrication of optical waveguides having a low light loss. The improved waveguides are obtained by the use of a smoothing layer over the rough etched sides of a waveguiding channel.
There is continuing interest in the development of new and improved techniques for the fabrication of organic optical waveguides which overcome some of the inherent deficiencies of optical waveguide formations in transparent organic media.
Accordingly, it is an object of this invention to provide an improved method for the production of organic optical waveguides.
It is another object of this invention to provide a method for the production of polymeric optical waveguides with a two-dimensional channel or rib waveguiding structure.
It is a further object of this invention to provide process embodiments for the production of polymeric optical waveguides having a smooth-wall channel or rib structure which exhibits low optical loss under wave propagating conditions.
Other objects and advantages of the present invention shall become apparent from the accompanying description and Examples.